This invention relates to hydrostatic transmissions (HSTs) and integrated hydrostatic transaxles (IHTs) where the HST is in a common housing with output gearing, a differential, output axles and the like. The general design of an IHT is known, and is disclosed in U.S. Pat. Nos. 5,314,387 and 6,185,936, the terms of which are incorporated herein in their entirety. Such IHTs are generally used with lawn and garden tractors and similar low speed vehicles.
Hydrostatic technology has also been used in higher speed vehicles such as utility vehicles, but such vehicles generally use a system having a plurality of hydrostatic pumps connected to a plurality of wheel motors each driving an independent wheel. Furthermore, while such pumps and wheel motors have been used, the most typical method of propulsion in such utility vehicles uses a variable sheave to change the speed into the transmission. The former system is disadvantageous because of the complex valves and controls involved in controlling flow to the wheel motors. The latter system suffers from inconsistent transmission of torque, high maintenance costs, and lower performance under some wet conditions.